An Airy-type model describes well the transition from thick continental crust to thin oceanic crust at rifted continental margins (Worzel, 1968), while a Pratt-type model is a better descriptor for the lateral density changes that occur at transform faults and fracture zones (Sibuet et al., 1974) and mid-ocean ridges (Lambeck, 1972). Hayford ( 1909), Bowie ( 1922), and Heiskanen ( 1931), among others, used the gravity field to determine the degree to which mountain ranges and ocean basins approach idealized local models of isostasy such as Airy's and Pratt's. It has been known since the turn of the last century that the gravity field and its relationship to topography is a critical constraint on the state of isostasy and the degree of compensation of Earth's surface features. All isostatic models underpredict the spectra at 2 < n < 12 and so we interpret the low-order Earth's gravity field as caused, at least in part, by nonisostatic processes due to dynamic motions such as those associated with convective upwellings and downwellings in Earth's mantle. Power spectra reveal that the gravity effect of topography and its flexural compensation contribute significantly to the observed free-air gravity anomaly spectra for spherical harmonic degree 33 400) and lower ( n < 33) degrees, but topography appears either uncompensated or fully compensated at these degrees, irrespective of the actual T e.

We have used spherical harmonic coefficients that describe Earth's gravity anomaly and topography fields to quantify the role of isostasy in contributing to crustal and upper mantle structure.

Himalaya flexture watts